In undifferentiated shock, a haemoglobin or haematocrit that is climbing rather than falling is a specific and frequently missed signal. It means plasma is leaving the circulation while red cells stay behind — capillary leak, not haemorrhage.
In Indian practice the commonest cause is dengue, where a rising haematocrit with falling platelets marks the critical phase and is the trigger for careful, titrated fluid resuscitation rather than generous boluses. The same physiology appears in hantavirus cardiopulmonary syndrome, in severe sepsis with profound leak, and in the systemic capillary leak syndromes.
The management consequence is specific. These patients need fluid, but they need it in small, reassessed aliquots, because most of what you give will end up in the lung and the interstitium rather than the circulation. The patient who is given four litres of crystalloid on the assumption that shock equals hypovolaemia arrives at intubation earlier than they had to.
So look at the trend, not the value: serial haematocrit alongside serial platelets, and a low threshold for point-of-care ultrasound to see whether the lungs are already wet.
- Compare serial haematocrit values; a single result tells you nothing
- A rising haematocrit with falling platelets in a febrile patient is dengue until proven otherwise
- Give fluid in small aliquots with reassessment, not as large boluses
- Use lung ultrasound early to see whether the interstitium is already filling
- Record the trend explicitly in the notes so the next clinician does not restart large-volume resuscitation
Why it matters
The reflex to treat shock with volume is right most of the time and specifically harmful in the group this sign identifies.
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